1. Field of the Invention
This invention relates to stretchable nonwoven sheets suitable for use in the manufacture of personal hygiene articles. More specifically, the stretchable nonwoven sheets are formed by substantially uniformly impregnating a necked nonwoven substrate or an easily extensible as-made nonwoven substrate with an elastomeric polymer.
2. Description of Related Art
Elastic nonwoven materials are well known in the art. Examples of elastic nonwoven materials include “stretch-bonded” and “neck-bonded” laminates. Stretch-bonded laminates are prepared by joining a gatherable layer to an elastic layer while the elastic layer is in an extended condition so that upon relaxing the layers, the gatherable layer is gathered. Neck-bonded laminates are produced by joining a necked, non-elastic layer with an elastic film on fiber layer. The elastic layer generally comprises an elastic film or an elastic nonwoven web. These elastic nonwoven laminates require the preparation of at least two separate nonwoven or film layers.
U.S. Pat. No. 4,366,814 to Riedel (Riedel) describes a breathable elastic bandage material comprising at least 50 weight percent of an extensible fabric capable of an elongation of at least 30% without tearing and at least 15 weight percent of an elastomer impregnated in the fabric without filling the holes in the fabric.
U.S. Pat. No. 5,910,224 to Morman (Morman) describes a method for making a stretchable composite by applying an elastomeric precursor to a neckable material such as a nonwoven web, neck stretching the neckable material and treating the elastomeric precursor, such as by heating, while the neckable material is in a necked condition to form an elastomeric layer bonded to the necked material. Preferred elastomeric precursors comprise a latex or a thermoset elastomer. The elastomeric precursor is applied to the neckable material in an amount between 5 g/m2 to about 50 g/m2. The elastomeric layer typically penetrates the web from about 2 to about 10 fiber thicknesses and the degree of penetration of the elastomeric precursor is controlled so that there is no strikethrough to the side of the web opposite the side on which the elastomeric layer has been applied. The resulting stretchable composite therefore has a film-like hand on the side comprising the elastomeric layer and retains the original soft hand of the neckable material on the side opposite the elastomeric layer.
Published European Patent Application No. 0472942 describes an elastomeric saturated nonwoven material having a compressibility and recovery in the Z-direction which includes a fibrous web, such as a nonwoven web of meltblown fibers, that is saturated with a polymeric material, such as an elastomeric acrylic latex, polyurethane latex, or nitrile rubber latex.
Published Japanese Patent Application No. 47-24479 is directed to belts for use in conveyors and power transmissions that are made by impregnating needlepunched nonwoven fabrics with rubber or synthetic resins.
There is a continued need for elastic sheet materials that can be produced economically, have soft stretch and good holding power, and which have a fabric-like hand on both surfaces.